Construction material or member



Marsh 17, 1970 E. T. STRICKLAND ETAL 3,501,048

CONSTRQTION MATERIAL OR MEMBER Filed Nov. 16, 1966 INVENTORS EDWARD T. STRICKLAND HOMER c. AMOS By fifi 41.4w, M57146 {W4 ATTORNEYS United States Patent 3,501,048 CONSTRUCTION MATERIAL 0R MEMBER Edward T. Strickland and Homer C. Amos, Palm Springs,

Califl, assignors to Brunswick Corporation, a corporation of Delaware Filed Nov. 16, 1966, Ser. No. 594,761 Int. Cl. B65d 7/42 US. Cl. 220-83 19 Claims ABSTRACT OF THE DISCLOSURE An article capable of withstanding high temperatures, said article being formed of filaments of a first material having a high modulus of elasticity and a high annealing temperature and a second material having a lower modulus of elasticity than that of said first material and a softening temperature below the annealing temperature of the first material with said second material diffusion bonding the said filaments together.

This invention relates to a construction material or member and more particularly to an improved elongate construction member, which when made into a laminate structure, such structure will have high physical strengths without creep when subjected to high temperatures for indefinite periods.

It is a general object of this invention to provide an improved composite construction material or member for use in apparatus having high temperature requirements above the temperature range available in known presentday plastics.

It is another object of this invention to provide a new and useful composite construction material or member which in one embodiment is formed of filaments of at least two different brittle materials.

Another object of this invention is to provide a composite construction material or member comprised of at least two different materials, one of which binds or molecularly bonds to the other to join the materials together in a laminate structure.

Still another object of this invention is to provide a new and useful elongate construction material or member having improved properties which can be used to form a high strength, high temperature resistant laminated article.

Still another object of this invention is to provide a new and improved compositional construction material or member which when made into a structure, the structure will become a quasi-flexible ceramic structure in which shock waves cannot be propagated.

Another object is to provide a compositional construction material or member which includes at least one primary filament of a high melting, high modulus of elasticity, vitreous material, which is structurally and dimensionally stable under the conditions'encountered in producing a rigid high temperature resistant vessel or article, and which also includes at least one secondary material of lower melting, lower modulus of elasticity, vitreous material having sufiicient molecular diffusion at a temperature below the annealing temperature of the primary filament to bind the filament and secondary material to gether and form the high temperature resistant laminated structure in which the primary filaments are substantially intact and retain their physical properties.

A further object is to provide a laminated vessel, article or structure, wound or otherwise fabricated, with one form of construction material or member laid up and joined at the contact points which forms bonds between the primary filaments and secondary materials less than 2 in width measured on the circumference of the primary filament.

And a further object is to provide an improved construction material or member wherein the ratio of the cross sectional area of the primary filaments to the cross sectional area of the secondary materials can vary between wide limits.

Still another object is to provide a construction material or member wherein the primary filament is in a strand or fiber form and the secondary material can be in fiber form or in powder or liquid form.

And yet another object is to produce a new and useful laminated vessel or other article from construction materials or members wherein the construction materials or members include a high temperature resistant, high modulus of elasticity, vitreous structural element and a lower melting, lower modulus of elasticity, vitreous material, and the superimposed cross layers of construction materials are joined at their points of contact to define a rigid high temperature resistant structure.

A further general object is to provide a method of making a heat-fused laminate article by laying up construe tion materials or members of any of the foregoing objects and sintering the laid-up structure to join the construction materials or members into a rigid structure by molecular diffusion.

Other objects and features of the invention will be apparent from the following description and from the drawings, in which:

FIGURE 1 is a fragmentary elevational view of a laminated vessel or the like embodying the invention, with some parts shown enlarged within a circle;

FIGURE 2 is an enlarged cross sectional view taken along the line 22 of FIGURE 1;

FIGURE 3 is a greatly enlarged fragmentary and somewhat diagrammatic showing of a sectional view through a construction material or member;

FIGURE 4 is a similar view through another form of construction material or member;

FIGURE 5 is a smaller but similar view through another form of construction material or member; and

FIGURE 6 is a view similar to FIGURE 5 only through still another form of construction material or member.

While we have shown in the drawings and shall describe in detail a few embodiments of the invention, it is contemplated that various changes may be made by those skilled in the art without departing from the spirit and scope of the invention.

In general terms, the present invention relates to a construction material or member composed of a first filament material which retains its high strength, high modulus of elasticity characteristics at high temperatures joined with a second material having a lower modulus of elasticity and which retains some reasonable strength at said high temperatures. Said high temperatures are of the type likely to be encountered by reentry vehicles, supersonic transports, rockets, high stress gas turbines and the like. By the combination of the strength and modulii of elasticity parameters, a construction material or member is produced having the unexpected results of transforming usually brittle state ceramics into quasi-flexible materials, producing in said construction material or member elongations and tensile strengths found rarely and erratically in monolithic structures and in single crystal filaments.

The construction material or member is the combination of a filamentized material which maintains its physical integrity at the highest temperature to which it would be subjected with a material or materials which may or may not be filamentized and which is part of the construction material or member and which has a low modulus of elasticity at the high temperature of use.

For illustration purposes, we have chosen to describe me improved construction material or member as being used to form a laminated vessel such as a radome or the like. FIGURE 1 shows a vessel which is substantially :onical in shape and has the layers or laminations 16, 17 :riss-crossed to form the Walls of the vessel. The construction material or member of our invention could be used to form a radome vessel by using the teaching of the US. Patent No. 3,031,361 in the name of E. T. Strickland, one of the co-inventors of the present subject matter. As shown in FIGURE 1, the vessel is formed on a. mandrel 18.

Each superimposed layer 16 or .17 is composed of a side-by-side uniformly laid-up series of construction materials or members which can best be seen in FIGURE 2 wherein the layers 16, 16 show the cross sectional view of one form of construction material or member 20 and the layers 17, 17 show the longitudinal view of said form of construction material or construction member 20.

One embodiment of the construction material or member 20 is shown in cross section in FIGURE 3 wherein a plurality of primary fibers or filaments 22 and a plurality of secondary materials which are shown as filaments 24, and which are in contact with and have a definite size relation to each other. Specifically, primary filament 22 is composed of a high strength, high modulus of elasticity, high temperature resistant, inorganic material that is structurally and dimensionally stable under the conditions encountered in producing a vessel. The secondary material in the form of filament 24 is composed of a different inorganic material which has a proportionately lower modulus of elasticity characteristics and is capable of molecularly bonding or joining to the material of the primary filament 22. The secondary material is such that, when it is in contact with a primary filament and the two are heated to a sintering temperature, there is a molecular diffusion of the secondary material with the primary filaments and/or other secondary materials at the points of contact to bind the filaments 22 and materials 24 together at such points of contact, as indicated in FIGURE 3 at 25. This sintering temperature is below the melting temperature of the secondary material and below the annealing temperature of the primary filament. The sintering temperature is selected to cause the secondary materials 24 to soften sufficiently to molecularly diffuse with the primary filament 22. The temperature is not high enough to cause the primary filaments to bond to each other. Therefore, all of the bonding action is between contacting secondary materials 24 and between secondary materials 24 in contact with primary filaments 22. At the sintering temperature there should be little or no chemical activity beween the two materials and the filamenting maerial must retain its filamentary form during sintering or other cohering process used to form the laminated structure. It is not intended that the construction material or construction member 20 which is composed of groups of primary filaments 22 and secondary materials 24 to be sintered until several cross layers of the construction materials or members 20 and laid up as in the process of producing laminated vessels or structures. It is recognized that there may be occasions when the construction material per se will be sintered before being laminated or otherwise put to use, but such a proceeding is within the scope of the invention even though not its principal application.

To create the most desirable construction material or member 20 for use in a laminated vessel 15 such as a radome and the like, it is desirable to hold filaments 22 and materials 24 without any twist or at the very most with a small amount of twist. Therefore, the contacts between adjacent secondary materials 24 when they are in the form of filaments and between secondary materials 24 and primary filaments 22 is generally somewhat linear along a line generally parallel to the axes of the filaments 22 and materials 24. Due to the linear lengthwise contact there will be a tendency for the bonds or contacts 25 to be over a relatively very small circumferential surface of the filaments. These bonds 25 between the adjacent secondary materials in the form of filaments 24 and between the secondary materials in the form of filaments 24 and primary filaments 22 create very strong construction material 20 after laminating and sintering. Each of the construction materials or members can be assembled in known manner from filaments formed by suitable apparatus.

Preferably, the ratio of the diameter of the primary filaments 22 to the diameter of the secondary materials in the form of filaments 24 is from 1:1 to 5:1. Also, in the preferred form of construction material or member, the primary filaments 22 occupy from 40% to of the cross sectional area of said structure with the secondary filaments 24 making up the balance.

FIGURE 3 shows the construction material or member 20 having the diameter of the primary filaments 22 five times the diameter of the secondary filaments 24. FIGURE 4 shows the ratio of diameters of the primary filament 22 to the secondary filament 24 to be 3:1, and FIGURE 5 shows a different form of construction material or member with diameters of primary filaments 22 to secondary 24 filaments having a ratio of 1:1.

FIGURE 6 shows a construction material or member 30 composed of a primary filament 32 and a secondary material in the form of a powder 34. The construction material or construction member 30 can be formed by drawing the primary filaments 32 through a well known fiber forming bushing. The primary filament 32 will be given an electrostatic charge as it emerges from the bushing and is then passed through a source of oppositely charged secondary material particles 34 in powder form. The particles 34 are attracted to and adhere to the primary filament 32 whereupon the joined mass is sprayed with a suitable sizing agent. The sizing agent or coupling agent can be one of the well known starch baths which when dry forms a binder to hold the secondary material powders 34 to the primary filament 32 during the laying up of the construction material 30 into a laminated structure or vessel. The laminated structure is then fired to a sintering temperature which burns out the starch and bonds the secondary material powders to each other and to the primary filament. When the secondary material is in the form of a liquid, it is applied to the primary filament by drawing the filament through a slurry of a suspension of finely divided particles such as a chlorinated dior tri-phenyl or similar material which evaporates without leaving a residue. The material will probably wet out under 200F. Several strands can be pulled through the slurry bath and wound or laid up into a laminated vessel.

As an example, a construction material or member 20 could have from 2,000 to 6,000 filaments, each one with a diameter of from .0002 to .0005 inch. The primary or structural filaments 22 can be made, for example, of alumina having approximately a 3700 F. melting point, with the secondary or binding material 24 being made of silica having approximately a 2700 F. melting point. The modulus of elasticity of the alumina is approximately 50 million pounds per square inch and of the silica is approximately 10 million pounds per square inch. With a plurality' of primary structural filaments 22 assembled with a plurality of secondary binding filaments 24 having a ratio of diameters of primary filaments 22 to secondary filaments 24 of 5:1, a loose bundle or group of filaments called a construction material or member is created.

The surface of the alumina material when used as the primary filament should be properly treated to prevent the surface from being dissolved by the softened silica at the sintering temperature. Such a treatment could be in the form of a metallic coating. It is more desirable to have a liquid phase during sintering (or curing) of the construction material to produce a more complete bonding.

Using the process of the above identified Patent No. 3,031,361, the construction material 20 can be laid up on the mandrel 18 such that the primary filaments 22 and secondary materials 24 will criss-cross each other between successive layers 16, 17 so as to form a multiplicity of points of contact there-between. When the several layers of construction materials have been completely laid up in the desired shape of the vessel, the resulting laid-up construction materials are sintered under suitable temperature and pressure conditions, e.g., at the sintering temperatures described hereinabove. The sintering temperature is sufficient to cause the secondary materials to molecularly diffuse at each point of contact with other secondary materials and with primary filaments so that the resulting structure consists essentially of a plurality of alternate longitudinal and peripheral layers of structurally and dimensionally stable primary filaments and secondary materials with the secondary materials bonding the primary filaments by molecular diffusion at contact points along the length of the construction materials and at points of cross-contact with other construction materials or members, thereby providing a rigid structure. The molecular diffusion of the secondary materials of each construction material is with the primary filaments and/or secondary materials of the other construction material or member at areas or points of longitudinal or transverse contact. Because of the high temperatures involved in sintering, the mandrel should be made of high temperature material and a suitable parting agent used on the mandrel.

Since it is contemplated that the materials from which the primary filaments and secondary materials are to be made will be such that temperatures up to the minimum sintering temperature of the secondary material will be quite high, the vessel will be susceptible of high temperature uses far beyond the previously available vessels. For instance, using the materials of our example above, with primary filaments made of alumina and secondary filaments made of silica, the construction material or member 20 and vessels made therefrom are capable of use at temperatures up to at least about 2500 F.

Accordingly, a vessel such as a radome made from construction materials using primary filaments and secondary materials as described will be very strong due to the multiplicity of molecular bonds between filaments and materials and will be usable at relatively high temperatures. In making the vessel, no additional bonding agents or filler will be needed to effect the molecular dilfusion, thereby simplifying the manufacturing of a vessel. Although the laid-up and sintered structure may include small air passages, these are reduced with increased laid-up thickness and are practically negligible for most high temperature applications, such as in radomes.

In some laminated structures, it may be desirable to have the interstices also filled in, probably with particles of the material forming the secondary material. It is also possible to have particles of material having various preselected dielectric constant characteristics which can be used to fill in the interstices so as to assist the designer in designing a product which meets more closely the demands of the specifications for the vessel.

The resulting laminated vessel will have the characteristic of dampening or preventing the propagation of shock stresses within the vessel due to the cross lamination of the construction materials or construction members. The individual materials going into making up the construction materials or members are each brittle and are susceptible to shock stress propagation but the combination of materials With their different modulus of elasticity characteristics and the application thereof in the present invention produces a construction that prevents shock stress propagation. The high modulus of elasticity of the primary material when combined with the lower modulus of elasticity of the secondary material prevents flutter instability of the resulting laminated f tligucture especially when used in a rocket casing or the Although alumina has been used herein as the high melting, high modulus of elasticity inorganic material, other materials may also be used in combination therew1th or as substitutes therefor. For example, the vitreous materlals commonly used for refractory applications can be melted and drawn into fibers in accordance with this invention. Such materials include such alumina silica materials as fireclays, kaolins, kyanite, sillimanite and topaz, many of which have fusion points as high as 2900- 3350 F. For example, a refractory vitreous material can have the following chemical composition: alumina- 51-55%, silica4347% and about 0.7l% each of Fe O and TiO and up to 0.5% alkaline earth oxides. Other useful high melting materials include vitreous silica Wl'llCh 1s provided by the fusion of high purity quartz or glass sand. These materials may be modified as needed by including other materials to enhance the drawability or formation of filaments from a melt.

Also, it is intended that other lower fusing, lower modulus of elasticity inorganic materials can be used in lieu of the silica referred to hereinabove. Although the silica is preferred because it is easy to handle as a melt the silica can be substituted in whole or in part by such other low fusing material as calcareous shale or argillaceous limestone, common shale, combinations of calcareous and siliceous materials such as metallurgical furnace slag. Such materials have a fusion point in the range of 15002500 F., and the fusion point can be lowered by adding varying amounts of a fiuxing material such as limestone, dolomite, fluorspar or feldspar. Also useful as low temperature glass are those thermoplastic vitreous compositions having an extremely low fusion or flowing temperature, not in excess of about 950 F. Glasses of this type are known in the art and include glasses having high phosphorus or lead content. Additional useful low fusion temperature glasses include alumlna silicate glass compositions containing from about 3 to about 20% manganese oxide, such as described by F. R. Charvat et al., in US. Patent 3,081,179, entitled Glass Fiber Composition.

Particularly preferred for the secondary materials are those vitreous materials which soften for molecular diffusion above 500 F. and below 2500 F. The materials for the primary filaments will usually have annealing temperatures below 4000 F.

Other modifications can be made as will be evident to those in the art. All percentages given herein are by weight unless otherwise indicated.

We claim:

1. A construction material or member comprising primary dimensionally stable structural filaments of a first vitreous material having a high modulus of elasticity and a high annealing temperature and secondary bonding materlal of a second vitreous material having a modulus of elasticity lower than that of said first vitreous material and a softening temperature below the annealing temperature of said first vitreous material and being attached to said first vitreous material.

2. The construction material or member of claim 1 wherein the ratio of the diameters of the filaments of the secondary bonding material: to the diameters of the filaments is in the range of from 1:1 to 1:5.

3. The construction material or member of claim 1 wherein the primary filaments comprise from 40% to of the total solid volume of the construction material.

4. The construction material or member of claim 1 wherein said second material has a softening temperature in the range of 500 F. to 2500 F.

5. The construction material of claim 1 wherein said second material is silica and said first material is alumina.

6. An article having a structural section formed from the construction material or member of claim 1 wherein said secondary materials are attached to the primary filaments by a molecular diffusion bond.

7. The article of claim 6 wherein each molecular diffusion bond extends over a small arc of the primary filaments.

8. The article of claim 6 wherein said secondary material is a filament and said primary and secondary filarnents are generally parallel to each other and are attched generally throughout their lengths.

9. The article of claim 8 wherein the filaments are attached throughout their lengths by molecular diffusion bonding.

10. A method of making a rigid laminate structure which is resistant to elevated temperatures, which method comprises laying up layers of-the construction member at claim 1 in such a manner as to provide alternate wherein the construction members have generally the same directional extent separated by layers wherein the construction members extend generally transversely to the construction members of said alternate layers and in compressive engagement with each other, and heating the layers to the softening temperature of said second vitreous material to produce molecular diffusion bonding by sintering between interengaging filaments.

11. The method of claim 10 wherein said construction members are laid up in tight contact with each other and in a sufficient number of layers to provide, on sintering, a substantially impervious wall structure.

12. A construction material or member comprising a primary dimensionally stable structural filament of a first inorganic material having a high annealing temperature and at least one secondary bonding filament of a second inorganic material, said second inorganic material having a softening temperature below the annealing temperature of said first inorganic material for bonding said secondary filaments to primary and secondary filaments by diffusion bonding while the primary filaments remain dimensionally stable.

13. The construction material of claim 12 composed of filaments of only two types, with one type being the primary filaments formed of a material having dimensional and structural stability when elevated to a sintering temperature, and the other type being the secondary filaments interspersed between the primary filaments and subject to molecular diffusion bonding with the primary filaments at said sintering temperature.

14. An article comprising a rigid structure formed of a plurality of superimposed layers of taut plural filament construction material laid up with the filaments of alternate layers in transverse relationship, said plural filament construction material comprising a secondary inorganic filament of a first material which has the property of sintering without melting at a sintering temperature and a primary inorganic filament of a second material'which is structurally and dimensionally stable at said sintering temperature, the annealing temperature of the primary filament being above said sintering temperature, said first material filaments being bonded to said primary filaments and having sufficient molecular diffusion at said sintering temperature to bind the primary and secondary filaments together and form a structure in which the primary filaments are substantially intact with molecularly diffused joints between said primary and secondary filaments throughout the structure and layers of the article.

15. The article of claim 14wherein the secondary filaments are bonded to the primary filaments by molecular diffusion defining a contacting bond area at each bond between the primary and secondary filaments less than two degrees measured on the circumference of the primary filaments.

16. The article of claim 14 wherein said rigid structure defines a radome.

17. The article of claim 14 wherein the composition of said primary inorganic filament is alumina and the composition of said secondary inorganic filament is silica.

18. A radome comprising a plurality of layers of filaments, each layer being composed of two different filamentized materials with one material being structurally and dimensionally stable when raised to an elevated tem perature and the other material being less structurally and dimensionally stable at such elevated temperature than said first mentioned material whereby upon elevating the temperature thereof a molecular diffusion between said materials bonding is effected, the filaments in one of the layers having a generally longitudinal extent relative to the axis of the radome, and the filaments of an adjacent layer extending generally transversely of the longitudinal filaments in superimposed relation with molecular diffusion bonding between said layers.

19. A hollow tubular article comprising superimposed layers of taut dual filament construction material alternate ones of said layers being helically wound about the article with the filaments thereof extending in the peripheral direction and alternate other layers of dual filament construction material being disposed with the filaments thereof extending longitudinally of said article, said construction materials forming layers of substantially uniform thickness and density of filaments, said dual filament material comprising primary filaments of a material which has a relatively high modulus of elasticity and is structurally and dimensionally stable under the temperature conditions encountered in producing and using the article, and secondary filaments of another material having a modulus of elasticity lower than that of said primary filaments and which when the dual filaments are heated to a temperature below the annealing temperature of the primary filaments, will have sufficient molecular diffusion upon contact to bind the filaments together and form a rigid structure in which the primary filaments are substantially intact and the contact areas between the primary and secondary filaments are relatively small as measured 011 the circumference of the primary filaments.

References Cited UNITED STATES PATENTS DONALD F. NORTON, Primary Examiner I. R. GARRETT, Assistant Examiner Us. 01. X.R. 

